All the forum posts I could find assumed access to either Windows or Linux machines to burn the firmware onto an SD card. I needed a couple of goes at this when trying from my Mac.
The main issue I had was how to remove and recreate one partition from the initial image.
i.e. how to grow that partition to use the remaining space on the SD Card. I found a way of using Virtualbox to do this as outlined below.
Finding the firmware
Grab the dd version of the image from [sipspeed downloads] (https://dl.sipeed.com/shareURL/MaixII/SDK/release)
Burning the initial image 1
MAKE SURE YOU ARE WRITING TO THE SD CARD
For me the SD Card showed up as /dev/rdisk2, be very careful to ensure you are writing to the SD Card and not a system disk.
sudo dd if=tina_v831-sipeed_uart0.img of=/dev/rdisk2 bs=1m
Expanding partitions on the image 1
In Virtualbox - mount the SD card in linux2
Pass the raw disk image over to Virtualbox :
sudo VBoxManage internalcommands createrawvmdk -filename /Users/goul/VirtualBox\ VMs/sdcard.vmdk -rawdisk /dev/disk2 sudo chown *<yourid> /dev/disk2
In virtuabox - add the raw disk to the ubuntu image using the storage manager.
Then extend the 5th partition using fdisk.
sudo fdisk /dev/sdb
(Delete any existing 5th partition - then add a new partition that is the remaining size of the disk.
Write changes to disk and then add file system via :
mkfs -t ext4 /dev/sdb5
The space added to this fifth partition will be later mounted as the /home partition on the device.